Looking for recommendations regarding use of LT-32 in my 256 Win Mag. If 16.5gr and 17.0gr of N120 are giving 2490fps and 2530fps respectively with a 70gr Sierra (I would consider these to be top-end loads), where would you recommend I start with Accurate LT-32? Case capacity of the 256 WM is 21.1gr of water, full case. My rifle is a custom built rifle and with a very well-cut chamber, not the oversized chamber many of the factory rifles received. Thank you.
N120/LT32 in 256 WM...
- Thread starter AlanF
- Start date
Jager
Gold $$ Contributor
No personal experience with the .256 Win Mag. But a curious anomaly...
QuickLoad, using the Sierra 70gr BlitzKing, COAL of 1.590, and your 21.1gr of case capacity, reports 100% charge density of N120 at 11.5gr. Your top load of 17.0gr would have a charge density of 146.9% !!!
Something's obviously amiss. You'd never remotely get all that powder into the case. And if you somehow could, you'd have pressures north of 90,000 psi.
For context, here's some load data from the May-June 1991 Handloader Magazine, No. 151...
And here is one cut at a powder chart out of QuickLoad...
N120 and LT-32 both seem very sub-optimal powders for this cartridge. And neither looks likely to achieve the velocities you're actually seeing. You sure that's N120 you've been using?
QuickLoad, using the Sierra 70gr BlitzKing, COAL of 1.590, and your 21.1gr of case capacity, reports 100% charge density of N120 at 11.5gr. Your top load of 17.0gr would have a charge density of 146.9% !!!
Something's obviously amiss. You'd never remotely get all that powder into the case. And if you somehow could, you'd have pressures north of 90,000 psi.
For context, here's some load data from the May-June 1991 Handloader Magazine, No. 151...
And here is one cut at a powder chart out of QuickLoad...
N120 and LT-32 both seem very sub-optimal powders for this cartridge. And neither looks likely to achieve the velocities you're actually seeing. You sure that's N120 you've been using?
Jager - Thank you for running the data. The largest case capacity I have read of for the 256 WM has been 22.0gr. However, even with the 21.1gr capacity I list, I show a capacity of 17.2gr with a flatbase bullet seated .30." This would fit my experience with numerous powders. One load that has been very stable in velocity and in SD has been 17.5gr of Reloder 7. Tested as high as 18.0gr but saw almost no velocity gain and a wider spread in numbers. According to the data these too would be impossible (to survive!). I wonder if some of the difference lies in a capacity difference from the old factory 256 brass and the cases formed from various 357Mag/360DW brass. My rifle is a custom with a minimum spec chamber as opposed to the over-sized, case destroying chambers on some of the older guns of which I have read but have no personal experience. A good reminder to carefully and diligently do our research and then load with the same considerations.
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